Cahill has long been touted as a target for Arsenal and Liverpool and there are plenty of others who are also interested in the possibility of luring the 25-year-old away from the Reebok Stadium.
After playing alongside Cahill for the past two years, Knight is acutely aware what a huge loss he would be.
However, such are the vast financial disparities that exist within the Premier League that Knight is realistic about what might happen in the coming weeks.
"You don't want to lose your best players and Gary is fantastic," said Knight.
"As yet, no one has come in for him, which is a blessing.
"We want to keep him but there are a lot of bigger clubs out there and if someone comes in for the right money, no one can stop him."
Not that Knight would view Cahill's departure as insurmountable.
David Wheater's arrival from Middlesbrough has already provided additional competition for places and, as the 31-year-old points out, with 69 Premier League starts from a possible 78 over the past two seasons, he has been a fairly consistent presence in the Trotters' line-up.
"Hopefully I have done enough to get my place on August 13," he said.
"David Wheater has given us additional options anyway but we have strengthened it up all over the park.
"If someone isn't playing too well the manager (Owen Coyle) can now bring people in."
Bolton appear to be having another push at trying to secure the services of Shaun Wright-Phillips from Manchester City, although wages could still prove a major stumbling block.
Interest in Liverpool striker David Ngog and Cameron Jerome of Birmingham has so far failed to turn into anything concrete, which means Bolton are set to tackle newly-promoted QPR at Loftus Road - if the violence in London has subsided by Saturday - with the men already at Coyle's disposal.
The Scot has certainly placed the Trotters on an upward trajectory since his arrival from Burnley a season and a half ago, although Knight still feels there is work ahead before they can be compared to the European qualifiers of Sam Allardyce's reign.
"We can't say yes on that until we get back into Europe, or finish in the top eight," said Knight.
"We are on our way there. We have made great strides forward since the manager came in, people who watch us play can see that.
"We dropped off a little bit towards the end of the season through fatigue but if we can have the same drive and determination, hopefully we can make it last.
"We want to get into Europe but we have to finish the season. We can't finish in March or April."